Friday night, a Norfolk Southern train consisting of about 50 railcars derailed in East Palestine, Ohio around 9 p.m. resulting in a massive fire.
The fire was large enough to be detected by the Pittsburgh, Pennsylvania radar for several hours Friday night. The video loop below shows that the fire first shows up around 9:20 p.m. last night.
The fire appeared to reach its peak intensity around 10:40 p.m. when brighter colors were showing up on radar and the smoke plume had traveled almost to Beaver Falls, PA. The radar detected a value of 31.5 decibels at 10:40 p.m. which would be equivalent to moderate rain/snow.
The smoke plume was blown to the south and east due to a northwest wind that was blowing over the fire.
Eventually, the wind direction changed to out of the south and you can see the smoke plume change directions in the video above.
Eventually, the fire decreased in intensity and stopped being visible on radar around 5:30 a.m.
How does radar detect smoke?
You might be surprised by the fact that the radar in Pittsburgh detected the fire. Usually, when people think of weather radars, they are thinking about how they are used to detect rain and snow.
However, weather radars have numerous non-meteorological uses such as detection of birds, insects and, in this case, smoke from fires.
Radars emit pulses of electromagnetic radiation in both a horizontal and vertical direction. This radiation travels roughly at the speed of light and it encounters clouds, bugs, precipitation and more along the way.
When the radar pulse interacts with these objects, a portion of it is reflected back to the radar dish and this is recorded as an echo. However, there is a caveat. The radars that the National Weather Service uses are designed specifically to detect precipitation sized particles. Raindrops have a diameter of 1-2 millimeters which are well within the detectable range of the radars that the National Weather Service uses.
Smoke particles are typically smaller than this, but larger fires can feature bigger smoke particles and the high density of smoke particles during such fires make them detectable using radar.
The fire in East Palestine produced enough of the larger sized smoke particles to be detected on radar. Even though the radar is no longer observing the larger smoke particles, the smaller particles are still in the atmosphere over parts of Ohio and Pennsylvania.
The southerly wind direction Saturday might blow some of those smoke particles back over Youngstown today. I will be on the lookout for any smoke on the weather cameras today.